Lamar Odom to 7-Year-Old Kid -- Don't Do Drugs

Do as he says, not as he does -- at least that was Lamar Odom's advice to a 7-year-old boy Saturday night ... when he warned him about the dangers of drug abuse.

Odom was at a birthday party at Tokyo Delves in North Hollywood -- along with about 20 people -- when the young boy named Elijah approached Odom to ask for a photo.

Elijah's mother tells us, Odom initially turned the kid down, offering to shake Elijah's hand instead and have a brief conversation ... which they did.

The mom says Lamar pontificated about the merits of education and staying in school -- and even encouraged Elijah (who is tall for his age) to play basketball -- but the ironic twist, Lamar finished the conversation by telling him, "Don't do drugs."

He then offered to take the above photo, despite previously refusing.